BACKGROUND: Interest in the study of body composition in childhood is increasing. Bioelectrical impedance analysis (BIA) is an accurate and reliable method. OBJECTIVES: To determine anthropometric parameters, fat-free body mass and fat body mass using BIA and anthropometry, and to establish their relationship. MATERIAL AND METHOD: A total of 365 healthy children (188 boys, 177 girls) aged 6.0 to 14.9 years were studied. Weight, height, arm circumference, skinfolds (bicipital, tricipital, subscapular and suprailiac) and bioelectrical parameters were measured. Body density was calculated from the four skinfold measurements using Brook’s formula. Bioelectrical impedance was measured with a BIA-101 S (RJL Systems) using a fixed frequency (50 kHz). Fat-free body mass from BIA was calculated using Deurenberg’s equation (FFM = 0.82 x height2/resistance). RESULTS: We present the mean, standard deviation and 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th and 97th percentiles of anthropometric variables and fat mass and fat-free mass estimated using BIA. Correlations were found between fat-free mass estimated using BIA and anthropometric variables. The reliability of BIA in estimating fat mass was assessed with intraclass correlation coefficients, which were excellent (0.948 in boys, and 0.945 in girls). CONCLUSIONS: BIA is an easy, low-cost, and highly reliable method, making it a useful technique for studying human body composition. This method shows excellent correlation with anthropometric variables.

OBJECTIVE: To compare the accuracy of percentage body fat (%BF) estimates between bioelectrical impedance analysis (BIA) and DXA in obese African-American women. RESEARCH METHODS AND PROCEDURES: Fifty-five obese African-American women (mean age, 45 years; mean BMI, 38; mean %BF, 48%) were studied. BF was assessed by both BIA (RJL Systems BIA 101Q; RJL Systems, Clinton Township, MI) and DXA (Hologic QDR-2000 Bone Densitometer; Hologic Inc., Bedford, MA). Generalized and ethnicity- and obese-specific equations were used to calculate %BF from the BIA. Bland-Altman analyses were used to compare the agreement between the BIA and the DXA, with the DXA serving as the criterion measure. RESULTS: Two of the generalized equations provided consistent estimates across the weight range in comparison with the DXA estimates, whereas most of the other equations increasingly underestimated %BF as BF increased. One of the generalized and one of the ethnicity-specific equations had mean differences that were not significantly different from the DXA value. DISCUSSION: The findings show that the Lukaski equation provided the most precise and accurate estimates of %BF in comparison with the QDR 2000 and provide preliminary support for the use of this equation for obese African-American women.

Journal of the American Dietetic Association. 2007 Aug;107(8):A29

Validation of Bioelectrical Impedance Against Dual-Energy X-Ray Absorptiometry in Adult, African American Females.

M.W. Valliant, D.K. Tidwell

The assessment of body composition (BC), specifically fat mass and fat-free mass is an important component of establishing nutritional status. Bioelectrical impedance (BIA) is a commonly used, non-invasive, low cost method to measure BC. African American (AA) females have a high rate of obesity so knowledge of BC is important to professionals working with this population. The objective of this study was to compare BIA (hand to foot model) to dual-energy X-ray absorptiometry (DXA) as the reference. BC was assessed by BIA (BIA 101 RJL System) and DXA (Hologic Delphi-W) in 100 healthy, AA females 18 – 40 years old with various body mass indices (range 17 – 47 kg/m2; mean = 29.53 +/- 6.86 s.d.). Both measures were completed in the morning following an overnight fast, physical inactivity for the previous 24 hours and in the supine position. Pearson.s correlation coefficient 0.94 (p = .01) indicated a strong correlation between the two methods and no significant statistical difference between the means (p = .72). Bland and Altman analysis showed strong agreement between the two methods across the range of body fat percentages indicating that they are comparable methods for measuring body fat percentage at lower and higher percentages of body fat. In conclusion, BIA is a suitable method to assess BC in adult AA females when factors such as food and beverage intake and physical activity are controlled.

BACKGROUND: The study of body composition in specific populations by techniques such as bio-impedance analysis (BIA) requires validation based on standard reference methods. The aim of this study was to develop and cross-validate a predictive equation for bioelectrical impedance using air displacement plethysmography (ADP) as standard method to measure body composition in Mexican adult men and women. METHODS: This study included 155 male and female subjects from northern Mexico, 20-50 years of age, from low, middle, and upper income levels. Body composition was measured by ADP. Body weight (BW, kg) and height (Ht, cm) were obtained by standard anthropometric techniques. Resistance, R (ohms) and reactance, Xc (ohms) were also measured. A random-split method was used to obtain two samples: one was used to derive the equation by the “all possible regressions” procedure and was cross-validated in the other sample to test predicted versus measured values of fat-free mass (FFM). RESULTS AND DISCUSSION: The final model was: FFM (kg) = 0.7374 * (Ht2 /R) + 0.1763 * (BW) – 0.1773 * (Age) + 0.1198 * (Xc) – 2.4658. R2 was 0.97; the square root of the mean square error (SRMSE) was 1.99 kg, and the pure error (PE) was 2.96. There was no difference between FFM predicted by the new equation (48.57 +/- 10.9 kg) and that measured by ADP (48.43 +/- 11.3 kg). The new equation did not differ from the line of identity, had a high R2 and a low SRMSE, and showed no significant bias (0.87 +/- 2.84 kg). CONCLUSION: The new bioelectrical impedance equation based on the two-compartment model (2C) was accurate, precise, and free of bias. This equation can be used to assess body composition and nutritional status in populations similar in anthropometric and physical characteristics to this sample.

Int J Obes Relat Metab Disord. 2000 Aug;24(8):982-8.

Estimation of body fat from anthropometry and bioelectrical impedance in Native American children.

OBJECTIVE: Obesity, as measured by body mass index, is highly prevalent in Native American children, yet there are no valid equations to estimate total body fatness for this population. This study was designed to develop equations to estimate percentage body fat from anthropometry and bioelectrical impedance as a critical part of Pathways, a multi-site study of primary prevention of obesity in Native American children. DESIGN: Percentage fat was estimated from deuterium oxide dilution in 98 Native American children (Pima/Maricopa, Tohono O’odham and White Mountain Apache tribes) between 8 and 11 y of age. The mean fat content (38.4%+/-8. 1%) was calculated assuming the water content of the fat-free body was 76%. Initial independent variables were height, weight, waist circumference, six skinfolds and whole-body resistance and reactance from bioelectrical impedance (BIA). RESULTS: Using all-possible-subsets regressions with the Mallows C (p) criterion, and with age and sex included in each regression model, waist circumference, calf and biceps skinfolds contributed least to the multiple regression analysis. The combination of weight, two skinfolds (any two out of the four best: triceps, suprailiac, subscapular and abdomen) and bioelectrical impedance variables provided excellent predictability. Equations without BIA variables yielded r2 almost as high as those with BIA variables. The recommended equation predicts percentage fat with a root mean square error=3.2% fat and an adjusted r2=0.840. CONCLUSION: The combination of anthropometry and BIA variables can be used to estimate total body fat in field studies of Native American children. The derived equation yields considerably higher percentage fat values than other skinfold equations in children.

OBJECTIVE: To compare the accuracy of percentage body fat (%BF) estimates between bioelectrical impedance analysis (BIA) and DXA in obese African-American women. RESEARCH METHODS AND PROCEDURES: Fifty-five obese African-American women (mean age, 45 years; mean BMI, 38; mean %BF, 48%) were studied. BF was assessed by both BIA (RJL Systems BIA 101Q; RJL Systems , Clinton Township, MI) and DXA (Hologic QDR-2000 Bone Densitometer; Hologic Inc., Bedford, MA). Generalized and ethnicity- and obese-specific equations were used to calculate %BF from the BIA. Bland-Altman analyses were used to compare the agreement between the BIA and the DXA, with the DXA serving as the criterion measure. RESULTS: Two of the generalized equations provided consistent estimates across the weight range in comparison with the DXA estimates, whereas most of the other equations increasingly underestimated %BF as BF increased. One of the generalized and one of the ethnicity-specific equations had mean differences that were not significantly different from the DXA value. DISCUSSION: The findings show that the Lukaski equation provided the most precise and accurate estimates of %BF in comparison with the QDR 2000 and provide preliminary support for the use of this equation for obese African-American women.

Acta Diabetol. 2003 Oct;40 Suppl 1:S246-9.

Validity of body composition methods across ethnic population groups.

Deurenberg P, Deurenberg-Yap M.

padeu@singnet.com.sg

Most in vivo body composition methods rely on assumptions that may vary among different population groups as well as within the same population group. The assumptions are based on in vitro body composition (carcass) analyses. The majority of body composition studies were performed on Caucasians and much of the information on validity methods and assumptions were available only for this ethnic group. It is assumed that these assumptions are also valid for other ethnic groups. However, if apparent differences across ethnic groups in body composition ‘constants’ and body composition ‘rules’ are not taken into account, biased information on body composition will be the result. This in turn may lead to misclassification of obesity or underweight at an individual as well as a population level. There is a need for more cross-ethnic population studies on body composition. Those studies should be carried out carefully, with adequate methodology and standardization for the obtained information to be valuable.

BACKGROUND: The study of body composition in specific populations by techniques such as bio-impedance analysis (BIA) requires validation based on standard reference methods. The aim of this study was to develop and cross-validate a predictive equation for bioelectrical impedance using air displacement plethysmography (ADP) as standard method to measure body composition in Mexican adult men and women. METHODS: This study included 155 male and female subjects from northern Mexico, 20-50 years of age, from low, middle, and upper income levels. Body composition was measured by ADP. Body weight (BW, kg) and height (Ht, cm) were obtained by standard anthropometric techniques. Resistance, R (ohms) and reactance, Xc (ohms) were also measured. A random-split method was used to obtain two samples: one was used to derive the equation by the “all possible regressions” procedure and was cross-validated in the other sample to test predicted versus measured values of fat-free mass (FFM). RESULTS AND DISCUSSION: The final model was: FFM (kg) = 0.7374 * (Ht2 /R) + 0.1763 * (BW) – 0.1773 * (Age) + 0.1198 * (Xc) – 2.4658. R2 was 0.97; the square root of the mean square error (SRMSE) was 1.99 kg, and the pure error (PE) was 2.96. There was no difference between FFM predicted by the new equation (48.57 +/- 10.9 kg) and that measured by ADP (48.43 +/- 11.3 kg). The new equation did not differ from the line of identity, had a high R2 and a low SRMSE, and showed no significant bias (0.87 +/- 2.84 kg). CONCLUSION: The new bioelectrical impedance equation based on the two-compartment model (2C) was accurate, precise, and free of bias. This equation can be used to assess body composition and nutritional status in populations similar in anthropometric and physical characteristics to this sample.

These papers and abstracts of papers have been published in peer-reviewed journals. They may draw conclusions and discuss applications of Bioelectrical Impedance Analysis which have not been reviewed by the FDA. Statements made within them are the sole responsibility of the authors. Unless otherwise indicated, no material support was provided to the authors or study investigators by RJL Systems.